Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.67	7.230%	$52.1888	$52.19	$52.20	$52.20
Purchase #2	$80.75	6.404%	$85.9212	$85.92	$85.90	$85.90
Purchase #3	$132.48	13.453%	$150.3025	$150.30	$150.30	$150.30
Purchase #4	$214.28	12.852%	$241.8193	$241.82	$241.80	$241.80
Purchase #5	$151.77	3.353%	$156.8588	$156.86	$156.85	$156.90
Purchase #6	$152.43	6.347%	$162.1047	$162.10	$162.10	$162.10
Purchase #7	$76.84	9.187%	$83.8993	$83.90	$83.90	$83.90
7 purchase totals =	$857.22		$933.0946	$933.09	$933.05	$933.10